Deaths among those working the nation’s oil and gas fields have risen at an alarming rate, the Associated Press has found.

At least 598 workers died on the job between 2002 and 2007, according to the U.S. Bureau of Labor Statistics. During that period, the number of deaths per year rose by around 70 percent, from 72 victims in 2002 to 125 in 2006 and a preliminary count of 120 in 2007.

The number of people laboring in the nation’s oil and gas fields has been soaring as part of a drilling boom that began in 2000-01, but that alone does not appear to explain the rising death toll, since the fatality rate – that is, the number killed relative to the number of workers – also climbed during the first half of the decade.

Many of those deaths have happened in Texas, the nation’s largest producer of crude oil and natural gas.

Experts blame several factors for pushing the toll ever higher in an industry long considered one of the most dangerous in the nation. Among them:

– A dramatic increase in drilling, spurred by record-breaking oil and natural gas prices. The number of workers in oil and gas jobs shot up from 290,000 in 2002 to 428,000 in 2007. In July 2002, 740 land-based oil and gas rigs were operating in the United States; today, there are about 2,000.

– An influx of new workers hired to operate all those rigs. Many of the newcomers are young, inexperienced and speak little English.

– A high-pressure environment where workplace safety lapses are common. Government agencies responsible for enforcing the rules rarely dole out tough penalties.

– Rampant drug and alcohol use among workers, some of whom turn to methamphetamine to get through 12-hour shifts and labor up to 14 days in a row